Have same issue on a 2016 Mk7 GTI with 70k miles.
Martins Garage would not fit new thermostat without an assessment charge of 1hr @ £150. Total estimate is an additional 3hrs labour plus cost of parts: £366 for thermostat housing and £82 for water pump. Total cost will be approx. £1200.
Decided to keep topping up as leak is very minor at the moment.
From below a small 'hanging' drip can be seen below the thermostat housing.
If it gets worse I will consider using a coolant sealant.
Another thought is....Why do garages insist on changing the housing when it is the seal that leaks ?